Petroleum residues have high viscosity and pour point that make them unsuitable as fuel in industrial furnaces and refineries. Moreover, the increased domestic and international demands of middle distillates and light fuel oil provide economic incentive to upgrade petroleum residues. Visbreaking, generally, is a non-catalytic petroleum refining process where the objective is to produce lighter products from heavy crude oil.
U.S. Pat. No. 6,540,904 discloses a process for upgradation of petroleum residue using Fe based catalyst along with almost 50% of water. However, the patent does not discuss the stability of the product.
U.S. Pat. No. 4,615,791 discloses a process for carrying out visbreaking operation at higher severity using hydrogen donor solvent for reducing the coke formation and producing a product of reduced viscosity, pour point and sedimentation characteristics.
U.S. Pat. No. 5,057,204 describes a process for increasing severity in visbreaking process using SeO2 as a catalyst, which helps in promoting transfer of hydrogen from residue feed to the portion of the feed having reactive radicals formed during the reaction. This patent does not disclose the use of hydrogen and aromatic rich material, which helps in increasing visbreaking unit severity by enhancing solvency power of the hydrocarbon oil for keeping asphaltenes in dispersed phase.
However, it is not possible to increase the visbreaking unit severity, as beyond a certain severity level, the bottom product from the visbreaking unit i.e. visbroken tar becomes unstable. Therefore, a need is always felt to develop a process, which can substantially increase the conversion in the visbreaking unit without making the visbroken tar unstable.